<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="UTF-8">
		<meta http-equiv="X-UA-Compatible" content="IE=edge">
		<meta name="viewport" content="width=device-width, initial-scale=1.0">
		<title>Document</title>
	</head>
	<body>
		<script>
			// 让用户输出一个整数n, 求 1!+2!+3!+4!+…n!。
			let n = window.prompt('请输入一个数字');
			let sum = 0;
			let temp = 1;
			for (let i = 1; i <= n; i++) {
				//temp = 1*1*2*3*4...*n;
				temp = temp * i;
				sum += temp;

			}
			console.log(sum);
		</script>
	</body>
</html>
